This invention relates to an article transport facility, and more particularly to an article transport facility having a plurality of mobile bodies movable forward and backward along a single track for transporting articles, and a control means for controlling operation of the mobile bodies. The invention relates also to a method of operating the facility.
The above article transport facility transports articles by reciprocal movement of each of the mobile bodies along a track. This facility realizes improved transport capacity by transporting articles with the plurality of mobile bodies.
A conventional article transport facility as noted above has two mobile bodies for moving forward and backward along the track. The control means is provided for controlling operation of the two mobile bodies to move and transport articles as separated from each other at least by a predetermined distance (see Japanese Patent Publication (Unexamined) H11-59819, for example).
In the conventional article transport facility, when the distance between the two mobile bodies moved in transporting articles becomes less than the predetermined distance, the two mobile bodies are stopped to avoid a collision.
Thus, the above conventional article transport facility, when moving the plurality of mobile bodies for article transport, does not permit the distance between the two mobile bodies adjoining longitudinally of the track to become less than the predetermined distance. In this case, there is a possibility that the plurality of mobile bodies cannot move efficiently for article transport.
When, for example, the two mobile bodies are moved in order to transport articles to two locations close to each other longitudinally of the track, the two mobile bodies are moved close to each other. When the distance between the two mobile bodies becomes less than the predetermined distance, the mobile bodies are stopped. Therefore, the mobile bodies cannot be moved efficiently for article transport. When an abnormality occurs with one of the mobile bodies, the abnormal mobile body cannot be moved by using the normal mobile body.
When the two mobile bodies standing still close to each other longitudinally of the track are moved to transport articles, for example, the mobile body located forward is first moved. The rearward mobile body is moved only after the two mobile bodies become spaced apart by the predetermined distance, In this way, it is necessary to perform a operation for making the distance between the two mobile bodies at least the predetermined distance, Thus, the plurality of mobile bodies cannot be moved efficiently for article transport.
In order to eliminate the above inconvenience, for example, a coupling device may be provided for coupling the two mobile bodies. When moving the two mobile bodies for article transport, the two mobile bodies may be coupled by the coupling device to move together. In this case, however, the coupling device must be attached to and detached from the mobile bodies manually. This operation is time-consuming, and consequently the plurality of mobile bodies cannot be moved efficiently for article transport.
In order to move the two mobile bodies together for article transport, it is also conceivable to attach a coupling device with an actuator to the mobile bodies, so that the mobile bodies are coupled by operation of the actuator. In this case, the coupling device with the actuator must newly be provided for the mobile bodies, resulting in a complicated construction.